This invention relates to polyprotein constructs and in particular polyprotein constructs comprising a plurality of papillomavirus (PV) amino acid sequences which may be used in compositions for eliciting an immune response against PV, and particularly human papillomavirus (HPV), in a host animal.
Papillomaviruses induce benign hyperproliferative lesions in humans and in many animal species, some of which undergo malignant conversion. The biology of papillomavirus infection is summarised in a review by J. P. Sundberg, entitled xe2x80x9cPapillomavirus Infections in Animalsxe2x80x9d In xe2x80x9cPapillomaviruses and Human Diseasexe2x80x9d edited by K. Syrjanen, L. Gissmann and L. G. Koss, Springer Verlag (1987).
Papillomaviruses are a family of small DNA viruses encoding up to eight early (E1, E2, E3, E4, E5, E6, E7 and E8) and two late genes (L1 and L2). These viruses have been classified in several distinct groups such as HPV which are differentiated into types 1 to xcx9c70 depending upon DNA sequence homology. A clinicopathological grouping of HPV and the malignant potential of the lesions with which they are most frequently associated are summarised in xe2x80x9cPapillomaviruses and Human Cancerxe2x80x9d by H. Pfister, CRC Press, Inc. (1990). For example, HPV type 1 (HPV-1) is present in plantar warts, HPV-6 or HPV-11 are associated with condylomata acuminata (anogenital warts), and HPV-16 or HPV-18 are common in pre-malignant and malignant lesions of the cervical squamous epithelium.
The immunological approach to the prevention of HPV disease requires a thorough analysis of the viral proteins against which humoral and cellular immune responses are mounted during and after infection. However, despite recent limited success (Kreider et al., 1986, J. Virol., 59, 369; Sterling et al., 1990, J. Virol., 64, 6305; Meyers et al., 1992, Science, 257, 971; Dollard et al., 1992, Genes and Development, 6, 1131), papillomaviruses are notoriously refractory to growth in cultured cells (Teichaman and LaPorta, 1987 In xe2x80x9cThe Papovaviridaexe2x80x9d, Vol 2 edited by N. P. Salzman and P.M. Howley, p.109). As a consequence, the lack of viral reagents has delayed the analysis of the immune response to PV infection.
The recent advent of recombinant expression systems in vitro has allowed the production of viral proteins encoded by both early and late genes in relatively large amounts and in a purified form (Tindle et al., 1990, J. Gen. Virol., 71, 1347; Jarrett et al., 1991, Virology, 184, 33; Ghim et al., 1992, Virology, 190, 548; Stacey et al., 1991, J. Gen. Virol., 73, 2337). These systems have, for the first time, allowed the analysis of the host immune response to these viral proteins.
Interest in immune responses to the non-structural early open reading frame (ORF) proteins of HPV has centred on HPV-16 E7 because of an apparent association between serum antibodies to this protein and cervical cancer (for a review, see xe2x80x9cImmune Response to Human Papillomaviruses and the Prospects of Human Papillomavirus-Specific Immunisationxe2x80x9d by Tindle and Frazer In xe2x80x9cHuman Pathogenic Papillomavirusesxe2x80x9d edited by H. zur Hausen, Current Topics in Microbiology Immunology, 186, Springer-Verlag, Berlin, 1994).
The immune responses to other HPV early ORF proteins have also been investigated including HPV-16 E6 (Stacey et al., 1992, J. Gen. Virol., 73, 2337; Bleul et al., 1991, J. Clin. Microbiol., 29, 1579; Dillner, 1990, Int. J. Cancer, 46, 703; and Mxc3xcller et al., 1992, Virology, 187, 508), HPV-16 E2 (Dillner et al., 1989 Proc.Natl. Acad. Sci.USA, 86, 3838; Dillner, 1990, supra; Lehtinen et al., 1992, J. Med. Virol., 37, 180; Mann et al., 1990, Cancer Res., 50, 7815; and Jenison et al., 1990, J. Infect. Dis., 162, 60) and HPV-16 E4 (Kxc3x6chel et al., 1991, Int. J. Cancer, 48, 682; Jochmus-Kudielka et al., 1989, JNCI, 81, 1698; and Barber et al., 1992, Cancer Immunol. Immunother., 35, 33). However, comparison of these studies reveals a lack of correlation between the results of the various assays which have been used in assessing HPV early ORF protein reactivity in serum (Tindle and Frazer, 1994, supra).
In addition, antibodies to other HPV early ORF proteins have not yet been sought with sufficient rigour in large enough numbers of patients to determine their utility as disease markers or as indicators of HPV protein immunogenicity following HPV infection.
A problem associated with immunising animals with preparations of individual PV proteins is that most of these proteins are comparatively small and might therefore not comprise many reactive epitopes. In addition, immunodominance of particular B or T cell epitopes within a single PV protein would vary presumably between animals of different major histocompatibility (MHC) backgrounds. To this end, the efficacy of such immunogens, in respect of eliciting an immune response against PV, might be expected to differ between animals of diverse MHC background.
In addition, there is surprisingly little knowledge regarding which PV proteins are expressed by infected cells at various stages of differentiation, and hence it is not possible to predict which proteins will be responsible for defining appropriate immunological targets.
The present invention provides a polyprotein construct comprising a plurality of PV early ORF proteins in one fused or linked construct to improve the efficacy of immune stimulation against PV infection and to avoid the need to define specific immunological targets.
In one aspect, the present invention provides as an isolated product, a polyprotein construct comprising at least two amino acid sequences fused directly or indirectly together, each of said sequences being the sequence of an early open reading frame (ORF) protein of papillomavirus (PV) or an immunogenic variant or fragment thereof, and at least one of said sequences being other than the E6 or E7 protein sequence or an immunogenic variant or fragment thereof.
In yet another aspect, the present invention provides a composition for eliciting a humoral and/or cellular immune response against PV in a host animal, said composition comprising an immunologically effective amount of a construct as described above, together with a pharmaceutically acceptable carrier and/or diluent.
In yet another aspect, this invention provides a method for eliciting a humoral and/or cellular response against PV in a host animal, which method comprises administering to the host animal an immunologically effective amount of a polyprotein construct as described above. In a related aspect, the invention also extends to use of such a polyprotein construct in eliciting an immune response against PV in a host animal. Preferably, the host animal is a human, however the host animal may also be a non-human mammal.
The present invention also extends to a nucleic acid molecule which encodes a polypeptide construct as broadly described above. Such a nucleic acid molecule may be delivered to a host animal in a nucleic acid vaccine composition with a pharmaceutically acceptable carrier and/or diluent, for expression of the encoded polyprotein construct in vivo in a host animal. Alternatively, the nucleic acid molecule may be included in a recombinant DNA molecule comprising an expression control sequence operatively linked to the nucleic acid molecule.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word xe2x80x9ccomprisexe2x80x9d, or variations such as xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprisingxe2x80x9d, will be understood to imply the inclusion of a stated integer or group or integers but not the exclusion of any other integer or group of integers.xe2x80x9d
The term xe2x80x9cpolyprotein constructxe2x80x9d as used herein is used to describe a protein construct made up of individual proteins that have been joined together in a sequence whereby they retain their original relevant biological activities.
The term xe2x80x9cisolatedxe2x80x9d as used herein denotes that the polyprotein construct has undergone at least one purification or isolation step, and preferably is in a form suitable for administration to a host animal.
By use of the term xe2x80x9cimmunologically effective amountxe2x80x9d herein in the context of treatment of PV infection, it is meant that the administration of that amount to an individual PV infected host, either in a single dose or as part of a series, that is effective for treatment of PV infection. By the use of the term xe2x80x9cimmunologically effective amountxe2x80x9d herein in the context of prevention of PV infection, it is meant that the administration of that amount to an individual host, either in a single dose or as part of a series, that is effective to delay, inhibit, treat or prevent PV infection or disease. The effective amount varies depending upon the health and physical condition of the individual to be treated, the taxonomic group of individual to be treated, the capacity of the individual""s immune system to synthesise antibodies, the degree of protection desired, the formulation of the immunogen, the assessment of the medical situation, and other relevant factors. It is expected that the amount will fall in a relatively broad range that can be determined through routine trials.
Preferably, the amino acid sequences in the polyprotein construct substantially correspond to the sequences of wild-type early ORF proteins of PV, including allelic or other variants thereof. Suitable variants include variants having single or multiple amino acid substitutions or additions to the wild-type sequences, and may have at least 50-60%, more preferably at least 70-80%, and most preferably at least 90%, similarity to the wild-type amino acid sequences, provided the variant is capable of eliciting an immune response against PV in a host animal. The amino acid sequences may also be immunogenic fragments of the wild-type early ORF proteins, that is fragments of the proteins which are capable of eliciting an immune response in a host animal. Suitably, the immunogenic fragment will comprise at least five, and more preferably at least ten, contiguous amino acid residues of the particular protein. Such immunogenic fragments may also be recognised by PV-specific antibodies, particularly antibodies which have a protective or therapeutic effect in relation to PV infection. Preferably, the immunogenic fragment is a non-full length fragment of a wild-type amino acid sequence, which may for example comprise a deletion mutant of an early ORF protein corresponding to at least 50%, more preferably 60-70%, and even 80-90% of the full length wild-type amino acid sequence.
The amino acid sequences in the polyprotein construct of the present invention may be selected from the group consisting of the E1, E2, E3, E4, E5 (E5a, E5b), E6, E7 and E8 proteins of PV, and may be included in the construct in any desired order. By way of example, the construct may be selected from the group consisting of:
(a) E6/E4
(b) E6/E5a/E4
(c) E6/E7/E4
(d) E6/E7/E5a/E4
(e) E6/E7/E1/E4
(f) E6/E7/E5a/E1/E4
(g) E6/E7/E5a/E1/E2/E4
(h) E6/E7/E5a/E5b/E1/E2/E4
(i) E2/E5b
(j) E2/E1/E5b
(k) E2/E5a/E5b
(I) E2/E1/E5a/E5b
(m) E2/E4/E5a/E5b/E6/E7/E1
(n) E2/E3/E4/E5/E8/E6/E7/E1.
As described above, at least one of the early ORF proteins is other than the E6 or E7 proteins. Preferably one of the early ORF proteins in the construct is the E4 protein.
The polyprotein constructs of this invention preferably comprise at least three, and more preferably three, four or five early ORF protein sequences. In addition, two or more different polyprotein constructs based on different combinations of early ORF proteins and/or different PV genotypes may be included in a single composition for prophylactic or therapeutic use.
In the polyprotein constructs of this invention, the amino acid sequences may be fused or linked directly together. Alternatively, they may be linked with a linker sequence of from 1 to 50, preferably 1 to 20, and more preferably 1 to 5, amino acid residues between the separate amino acid sequences. By way of example, such a linker sequence may be an amino acid sequence encoded by the nucleotide sequence comprising a restriction endonuclease site. Linker sequences as described above may also be provided before and/or after the amino acid sequences in the polyprotein constructs.
The polyprotein constructs of this invention may also comprise a tag protein or peptide moiety fused or otherwise coupled thereto to assist in purification of the polyprotein construct. Suitable tag moieties include, for example, (SEQ ID. NO:47) (His)6, glutathione-S-transferase (GST) and FLAG (International Biotechnologies), with the (His)6 tag moiety being preferred. The constructs may further comprise a component to enhance the immunogenicity of the polyprotein. The component may be an adjuvant such as diphtheria or cholera toxin or E. coli heat labile toxin (LT), or a non-toxic derivative thereof such as the holotoxoid or B subunit of cholera toxin or LT. In addition, the polyprotein construct of the invention may comprise a lipid binding region to facilitate incorporation into ISCOMs. Suitable lipid binding regions are disclosed by way of example in Australian Provisional Patent Application No. PN8867/96, dated Mar. 25, 1996. A preferred lipid binding region is an influenza haemagglutinin tail.
The present invention also provides a nucleic acid molecule comprising sequence of nucleotides which encodes a polyprotein construct as broadly described above.
The nucleic acid molecule may be RNA or DNA, single stranded or double stranded, in linear or covalently closed circular form. It will be appreciated that the sequence of nucleotides of this aspect of the invention may be obtained from natural, synthetic or semi-synthetic sources; furthermore, this nucleotide sequence may be a naturally-occurring sequence, or it may be related by mutation, including single or multiple base substitutions, deletions, insertions and inversions, to such a naturally-occurring sequence, provided always that the nucleic acid molecule comprising such a sequence is capable of being expressed as a polyprotein construct as described herein.
The nucleotide sequence may have expression control sequences positioned adjacent to it, such control sequences being derived from either a homologous or a heterologous source.
Since nucleic acid molecules may be delivered directly as xe2x80x9cnaked DNAxe2x80x9d to a host animal, (see, for example, Wolfe et al., 1990, Science 247:1465 and Fynan et al., 1993, Proc.Natl. Acad. Sci. USA, 90:11478), the present invention also includes a nucleic acid vaccine composition comprising a nucleic acid molecule as described above, together with a pharmaceutically acceptable carrier and/or diluent.
Immunisation with an isolated nucleic acid molecule allows in vivo synthesis of the encoded polyprotein construct by the host animal in a manner similar to the manner in which PV proteins are expressed during infection by PV. In this aspect, the present invention also extends to a method for eliciting an immune response against PV in a host animal, which method comprises administering to the host animal an immunologically effective amount of a nucleic acid molecule as described above. The invention also extends to use of such a nucleic acid molecule in eliciting an immune response against PV in a host animal.
This invention also provides a recombinant DNA molecule comprising an expression control sequence having promoter and initiator sequences, the nucleotide sequence encoding the polyprotein construct being located 3xe2x80x2 to the promoter and initiator sequences and a terminator sequence located 3xe2x80x2 to this sequence of nucleotides. In yet another aspect, the invention provides a recombinant DNA cloning vehicle such as a plasmid capable of expressing the polyprotein construct, as well as a host cell containing a recombinant DNA cloning vehicle and/or a recombinant DNA molecule as described above.
Suitable expression control sequences and host cell/cloning vehicle combinations are well known in the art, and are described by way of example, in Sambrook et al. (1989) Molecular Cloning: A Laboratory Manual, 2nd ed. Cold Spring Harbor, N.Y. Cold Spring Harbor Laboratory Press. Thus, the nucleotide sequence may be ligated into any suitable expression vector, which may be either a prokaryotic or eukaryotic expression vector. Preferably, the vector is a prokaryotic expression vector such as pTrcHisA or pGEX-STOP (a pGEX expression vector (Amrad/Pharmacia Biotech) which has been manipulated so as to result in truncation of the GST moiety, disclosed in Australian Provisional Patent Application No. PN8272/86, dated Feb. 26, 1996). Whilst the host cell is preferably a prokaryotic cell, more preferably a bacterium such as E. coli, it will be understood that the host cell may alternatively be a yeast or other eukaryotic cell, or insect cells infected with baculovirus or the like.
Once recombinant DNA cloning vehicles and/or host cells expressing a polyprotein construct of this invention have been identified, the expressed polypeptides synthesised by the host cells, for example, as a fusion protein, can be isolated substantially free of contaminating host cell components by techniques well known to those skilled in the art.
The polyprotein construct-encoding DNA sequence is formed by linking or xe2x80x9cfusingxe2x80x9d sequences encoding each of the individual protein moieties. The first sequence in the polyprotein DNA construction has a promoter element and a ribosome binding site. These elements assure that transcription of the polyprotein DNA into mRNA begins at a defined site and that the signal, the ribosome binding site, needed for translation of mRNA into protein is present. Synthesis of the polyprotein is made continuous from one protein component to the next by removing or altering any initiation or binding signals and stop codons from the subsequent protein-encoding sequences. The stop codon, normally a signal for the ribosome to stop translation and to end the polypeptide, is not altered or removed from the last DNA sequence. The individual protein encoding sequences are jointed such that a proper phasing is made of the mRNA reading frames for translation of the sequence into the desired amino acids. Once a DNA sequence encoding a polyprotein construct or a xe2x80x9cpolyprotein genexe2x80x9d is made, it is necessary to demonstrate that the construction leads to production of a stable polyprotein construct. If the resulting protein is not stable, for example because the junctions between the proteins are vulnerable to proteolytic digestion, then the junction regions are modified. This can be done by inserting different amino acids at or near the junction or by building spacers of amino acids between the individual proteins. Linkers or spacers can also be introduced to modify the overall activity of the polyprotein. By adjusting the space between and orientation of the individual proteins it is possible to modify the total activity of the polyprotein construct. Further details of the preparation of polyprotein constructs of the present invention by recombinant DNA techniques are disclosed, by way of example, in U.S. Pat. No. No. 4,774,180, the disclosure of which is incorporated herein by reference.
Preferably, the polymerase chain reaction (PCR) is used to amplify the nucleotide sequences encoding each of the individual PV early ORF proteins. The nucleotide sequences which are amplified may be full length or non full-length fragments thereof. Restriction endonuclease sites may be incorporated in the oligonucleotide primers used for PCR to furnish directional ligation of the amplification products in the same translational frame and to enable directional cloning into a suitable expression vector. The primers may encode an artificial initiator codon or a termination codon.
The first nucleotide sequence has an initiator codon. This initiator codon may either be the normal wild-type initiator codon of the first sequence or may be inserted artificially at another chosen position of this sequence. Synthesis of the polyprotein construct is made continuous from one protein component to the next by removing or altering any initiation or binding signals and termination codons. The termination codon must be present in the last nucleotide sequence. This is effected normally by not altering or removing the termination codon of the last nucleotide sequence. However, this termination codon may be inserted artificially, by methods known to persons skilled in the art, by first removing the normal, wild-type termination codon of the last nucleotide sequence and inserting another, in the correct reading frame, at another position of this sequence.
The polyprotein construct-encoding DNA sequence may incorporate restriction sites at the flanking ends to facilitate insertion of the DNA sequence into a suitable expression vector.
The PV can be a human or an animal PV, and is preferably HPV. The HPV may be of any genotype, and may for example be selected from the group consisting of HPV-6, HPV-11, HPV-16, HPV-18, HPV-33, HPV-35, HPV-31 and HPV45. Preferably, the HPV is HPV-6 or HPV-11.
The present invention is particularly, but not exclusively, directed to polyprotein constructs comprising early ORF proteins of the HPV-6 and HPV-11 genotypes which are causative agents of condylomata acuminata, however it will be appreciated that the invention extends to variants of the corresponding proteins in other HPV genotypes, particularly the HPV-16 and HPV-18 genotypes, and other genotypes which have oncogenic potential of a type similar to HPV-16 and HPV-18.
The polyprotein constructs of the present invention may comprise early ORF proteins of a single HPV genotype, or alternatively they may comprise early ORF proteins from more than one HPV genotype. In addition, a combination of more than one polyprotein construct may be used in cases where not all early ORF proteins are represented in the one polyprotein construct, or where immune responses to more than one HPV genotype are desired.
The polyprotein constructs of the present invention are provided as isolated proteins, that is they are substantially free of other PV proteins, and find particular utility for the treatment of genital warts, cervical cancer or other conditions caused by HPV in man. The polyprotein constructs can be included in pharmaceutical compositions for the treatment or prevention of diseases involving HPV as well as the other conditions discussed above.
The polyprotein constructs of the invention may be used to raise antibodies and/or induce cellular immune responses, either in subjects for which protection against infection by PV is desired, i.e. as prophylactic vaccines, or to heighten the immune response to an PV infection already present, i.e. as therapeutic vaccines. They also can be injected into production species to obtain antisera. In lieu of the polyclonal antisera obtained in the production species, monoclonal antibodies may be produced using the standard methods or by more recent modifications thereof by immortalising spleen or other antibody-producing cells for injection into animals to obtain antibody-producing clones. The polyclonal or monoclonal antibodies obtained, corrected if necessary for species variations, can also be used as therapeutic agents.
Direct administration of the polyprotein constructs to a host animal such as a human can confer either protective immunity against PV or, if the subject is already infected, a boost to the subject""s own immune response to more effectively combat the progress of the PV induced disease.
The magnitude of the prophylactic or therapeutic dose of a polyprotein constructs of this invention will, of course, vary with the group of patients (age, sex, etc.), the nature or the severity of the condition to be treated and with the particular polyprotein construct and its route of administration. In general, the weekly dose range for use lies within tie range of from about 0.1 to about 5 xcexcg per kg body weight of a mammal.
Any suitable route of administration may be employed for providing a mammal, especially a human, with an effective dosage of a polyprotein construct of this invention. For example, oral, rectal, vaginal, topical, parenteral, ocular, nasal, sublingual, bucccal, intravenous and the like may be employed. Dosage forms include tablets, troches, dispersions, suspensions, solutions, capsules, creams, ointments, suppositories, aerosols and the like. Said dosage forms also include injected or implanted slow releasing devices specifically designed for this purpose or other forms of implants modified to additionally act in this fashion.
If the polyprotein constructs are to be administered as vaccines, they are formulated according to conventional methods for such administration to the subject to be protected. The polyprotein constructs may be delivered in accordance with this invention in ISCOMS(trademark) (immune stimulating complexes), liposomes or encapsulated in compounds such as acrylates or poly(DL-lactide-co-glycoside) to form microsphers. They may also be incorporated into oily emulsions and delivered orally.
Other adjuvants, as well as conventional pharmaceutically acceptable carriers, excipients, buffers or diluents, may also be included in vaccine compositions of this invention. Generally, a vaccine composition in accordance with the present invention will comprise an immunologically effective amount of the polyprotein construct, and optionally an adjuvant, in conjunction with one or more conventional pharmaceutically acceptable carriers and/or diluents. An extensive though not exhaustive list of adjuvants can be found in Coulter and Cox, xe2x80x9cAdvances in Adjuvant Technology and Applicationxe2x80x9d, in Animal Parasite Control Utilizing Biotechnology, Chapter 4, Ed. Young, W. K., CRC Press, 1992. As used herein xe2x80x9cpharmaceutically acceptable carriers and/or diluentsxe2x80x9d include any and all solvents, dispersion media, aqueous solutions, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutical active substances is well known in the art and is described by way of example in Remington""s Pharmaceutical Sciences, 18th Edition, Mack Publishing Company, Pennsylvania, U.S.A.
In practical use, a polyprotein construct of this invention can be combined as the active ingredient in intimate admixture with a pharmaceutical carrier according to conventional pharmaceutical compounding techniques. The carrier may take a wide variety of forms depending on the form of preparation desired for administration, e.g. oral or parenteral (including intravenous and intra-arterial). In preparing the compositions for oral dosage form, any of the usual pharmaceutical media may be employed, such as, for example, water glycols, oils, alcohols, flavouring agents, preservatives, colouring agents and the like in the case of oral liquid preparations, such as, for example, suspensions, elixirs and solutions; or carriers such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubricants, binders, disintegrating agents and the like in the case of oral solid preparations such as, for example, powders, capsules and tablets. Because of their ease of administration, tablets and capsules represent the most advantageous oral dosage unit form, in which case solid pharmaceutical carriers are obviously employed. If desired, tablets may be sugar-coated or enteric-coated by standard techniques.
In addition to the common dosage forms set out above, the polyprotein constructs of this invention may also be administered by controlled release means and/or delivery devices, including by way of example, the controlled release preparations disclosed in International Patent Specification No. PCT/AU93/00677 (Publication No. WO 94/15636)
Pharmaceutical compositions of the present invention suitable for oral or parenteral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient, as a powder or granules or as a solution or a suspension in an aqueous liquid, a non-aqueous liquid, an oil-in-water emulsion or a water-in-oil liquid emulsion. Such compositions may be prepared by any of the methods of pharmacy but all methods include the step of bringing into association the active ingredient with the carrier which constitutes one or more necessary ingredients. In general, the compositions are prepared by uniformly and intimately admixing the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired presentation.